Multilevel spray-drying apparatus

ABSTRACT

A means is provided for spray drying large volumes of a synthetic detergent slurry which comprises a means spraying the slurry into a spray-drying chamber in at least two different levels of uniformly spaced atomizing nozzles. The lowest level of nozzles is critically positioned at a point in the spray chamber below a 190* F. isotherm and above a boiling point isotherm. From 30 percent to 80 percent of the slurry is atomized at this lowest level. The balance of the same slurry is sprayed through the remaining levels. Means is provided at the bottom of the chamber for introducing a cyclonic current of heated drying gas, and a means is provided at the top of the chamber for exhausting the gas.

United States Patent inventors Appl. No. Filed Patented AssigneeMULTILEVEL SPRAY-DRYING APPARATUS 3 Claims, 2 Drawing Figs.

U.S.Cl

. References Cited UNITED STATES PATENTS 10/1926 Schwantes 34/174,34/168, 159/4 CC, l59lDIG. 14 Int. Cl F26b 17/12 Field of Search168,169,174; 159/4 CC, DIG. 14

Vertical Counter Current Dryers," Advances In Food Research, pp. 430-433, (2) 1949 Primary Examiner-Carroll B. Dority, Jr. Attorneys-JuliusP. Filcik and Richard C. Witte ABSTRACT: A means is provided for spraydrying large volumes of a synthetic detergent slurry which comprises ameans spraying the slurry into a spray-drying chamber in at least twodifferent levels of uniformly spaced atomizing nozzles. The lowest levelof nozzles is critically positioned at a point in the spray chamberbelow a 190 F. isotherm and above a boiling point isotherm. From 30percent to 80 percent of the slurry is atomized at this lowest level.The balance of the same slurry is sprayed through the remaining levels.Means is provided at the bottom of the chamber for introducing acyclonic current of heated drying gas, and a means is provided at thetop of the chamber for exhausting the gas.

CRUTCHER Io SLURRY PATENTED UEC28 1971 E N 4 O 3 Z 5 3 2 x 3 n U .U 3 0J by m 3 A T l w u m 2 m 0 l A 4 3 W 2 l R 1 n B B I 1 mm g M R N Uw 0Rs H C V R AE I INVENTORS Robert P. Davis Michoei S, Hoines John A.Sugel ATTORNEY MULTILEVEL SPRAY-DRYING APPARATUS BACKGROUND OF THEINVENTION l. Field of the Invention This invention relates to the art ofspray drying synthetic detergent aqueous slurries to form granularsynthetic detergent compositions.

2. Description of the Prior Art Practices This invention relates to alarge-volume operation involving spraying thousands of pounds per hour,hundreds of thousands of pounds per day. Ordinarily spray towers areused employing a single level of atomizing nozzles which are locatednear the top of the spray-drying chamber. Spray drying large volumes ofdetergent slurries is a complex procedure involving numerousinterrelated factors such as volume and rate of production, differentingredients which comprise a synthetic detergent slurry, difierentprocessing requirements and conditions, difierent characteristics of thenumerous ingredients, e.g., hydration properties, massive requirementsof drying air, the desired physical and performance properties of theeventual spray-dried product, leveling and packaging of finalspray-dried granular product.

SUMMARY OF THE INVENTION It has now been discovered that an ordinarysingle-level spray-drying method can be substantially improved withsurprising and unexpected results by employing multilevels of atomizingnozzles provided that certain important horizontal and verticalalignments are met together with compliance of important processingconditions.

As a result of practicing this invention, it is possible tosignificantly increase the rate of production over ordinary singlelevelspray-drying operations. Improved rates can, for example, be on theorder of 10 percent to 30 percent. In the context of large-volumeproductions such magnitudes of rate improvement can represent millionsof pounds annually.

Surprisingly this increase in production rate is achieved without resortto more severe heat requirements. It was completely unexpected that thepresent multilevel spray-drying process would provide such increasedefficiency in heat utilization.

The present method has as another objective the advantage of providing asignificant measure of control over the density of the final driedgranules. By adhering to the teachings of this invention, it is possibleto decrease the density of certain compositions and to increase thedensity of other products. While the most frequent objective in ordinarycommercial practices is to produce granules of decreased density, thepresent invention provides a reasonable degree of flexibility inachieving greater densities also.

Surprisingly, the decrease in particle density is achieved even thoughthe average particle size is uniformly smaller. Normally, the finer thespray-dried particle size, the greater the density. Inspection ofproduct sieve fractions from the practice of this invention indicatesthat the specific density of the individual particles are significantlylower and that the individual granule shape is irregular. It isspeculated that the combination of these two observations offset thenormally expected density increase normally associated with overallfiner granular product.

Another unexpected advantage of the present invention is the substantialdecrease in the amount of fine powders and vaporous effluent materialsproduced by the method of the present invention. Reductions as high as50 percent have been found. The advantage of such an improvement interms of environmental control, i.e., air pollution is noteworthy. Notonly is fine powder production cut in half at the exhaust tower, butthere is additional improvement in the marked decrease in aerosol(vapor) contaminants which pass into the atmosphere. This improvement isone which is more difi'icult to measure and lends itself more readily tosubjective appraisal. Nevertheless, the improvement is real and canrepresent a significant advance in efiorts to improve and comply withclean air standards. The aerosol and vaporous effluents have thetendency to give permanence to steam and smoke plumes occasionally seencoming from spray tower facilities.

Moreover, in addition to the marked reduction of fine powders (overheaddusts) the present invention provides an equally significant reductionin heavy coarse products (tower tailings). Consequently, by minimizingproduction of fine powders and coarse granules, the manufacturer is ableto enjoy a proportional improvement in product satisfactory for packing.This provides an ultimate economic savings of substantial magnitude inthe context of the huge amounts of production contemplated.

A further unexpected result of the present invention is that each of theaforementioned advantages are provided without increasing the amount ofinsolubles formed by the spraying operation. Such insolubles are attimes referred to as floc and are formed, it is believed, by physicaland chemical degradations due to severe drying conditions. An essentialembodiment of the present invention as described below comprisesspraying a very substantial proportion of the detergent slurry into ahigh-temperature zone that was heretofore intentionally avoided bywidely practiced commercial spray-drying procedures. Thus it wasexpected that the exposure of freshly sprayed droplets to inordinatelyhigh temperatures would cause excessive formations of floc andinsolubles. This does not occur, however.

While the role of phosphates in detergent compositions is beingquestioned in temis of water quality, the outcome is still in doubt. Inany event the present invention provides a significant advance inspray-drying phosphate builders such as sodium tripolyphosphate. For along time, one of the widely held serious limitations in using higherspray-drying temperatures for phosphate-containing detergentcompositions was that overdrying caused a marked reversion of phosphatesto other less desirable phosphorus compounds such as pyrophosphates andorthophosphates. These latter materials are admittedly poorer detergencybuilders. The present multilevel spray-drying method is not handicappedby problems of such reversion. In fact, these is less reversion with thepresent invention than one finds with an ordinary single-levelspray-drying process.

Several unexpected advantages enjoyed by the present method areattributed to the overall less severe drying conditions which areemployed by the present invention. In this respect, one of the majorconcerns in an ordinary single-level spraying operation is overdryingthe freshly sprayed particles as they dry falling through the tower.Ordinarily the hottest zone, the area where the highest isotherms exist,is near the lowest region of the spray chamber. This is the point atwhich hot air is introduced and dispersed through plenum arrangements.The heated drying gas passes up through the tower countercurrently tothe falling atomized particles. As the atomized droplets fall throughthe rising air currents, they begin to dry. However, the removal ofwater is relatively slower in the upper tower regions which, while warm,is still cooler than the hotter lower regions. By the time the dropletsfall into the highest temperature zone, they have dried sufficiently tohave set and solidified to form granules having a hard surface skin. Itis these dried particles which by ordinary conventional practice muststill pass through the highest temperature zone. It is here thatoverdrying problems can occur. Phosphate reversion is just one of theseproblems. The degradation of other detergent additives such asbrighteners, amides, nonionic detergents, germicides is also known tooccur in this region. Such degrading action not only can adverselyafiect the overall performance effectiveness of the products but alsogive rise to unpleasant color and odor problems and other aestheticnegatives.

Surprisingly these overdrying problems are considerably alleviated bythe present invention. The exact reason for this is not known. What isbelieved to occur however, and this is reasoned speculation, is thatatomization of a portion of the crutcher mix into a zone intermediate aF. isotherm and a boiling point isotherm (the remainder of the mix beingatomized into zones of still lower temperature) results in a less severetimeltemperature exposure for the resulting product. In addition, thereis a sudden release of steam and gases, not heretofore experienced inprior art spray-drying operations, which tend to alter and beneficiallyeffect rising air currents. Thus, the particles freshly sprayed into thetop of the spray tower fall through and are exposed to a dryingenvironment materially different from anything previously known. Theconsequences are all of the beneficial results noted above as well asthe very significant improvement described below respecting spray dryingsynthetic detergent compositions containing low levels of phosphatebuilders or detergent compositions in which the phosphate builder hasbeen replaced partially or completely with a phosphate-free builder suchas sodium nitrilotriacetate (N'I'A), sodium citrate, sodium mellitate,sodium oxydiacetate, starch, cellulose, sugars and sugar derivatives,sodium oxydisuccinate and the like.

Because of the predominant role which sodium tripolyphosphate has heldas a detergency builder over the last three decades, the bulk ofspray-drying technology has developed naturally around that singlebuilder material. Now that considerable emphasis is being placed onfinding partial or total replacement of phosphates, the knownspray-drying techniques are being applied to new materials.

In arriving at the present invention, it has been discovered thatphosphate spray-drying technology does not uniformly apply to sodiumnitrilotriacetate and other phosphorus-free builder systems (the termsystems meaning broadly other sole builder replacements or mixtures ofsuch alternative materials). It was disappointing to discover thatexisting factory facilities and supporting engineering resources couldnot, carte blanche, be applied to, for instance, NTA-built systems.

One of the more important objectives of this invention therefore is toprovide a method and apparatus that successfully solves the severalproblems encountered in spray drying nitrilotriacetate builders, as soledetergent ingredients or as mixtures with sodium tripolyphosphate. Onesevere obstacle encountered in spray drying NTA/STP blends was thestickiness of the resulting granules. Handling such granules presented alarge problem. Transporting them, storing them and packaging them wasdifficult. The present invention, methodwise and apparatuswise, solvedeach of these problems in a highly reasonable and satisfactory manner.

As a result, whereas it was thought that major production rate cutbackswould be necessary with novel built detergent compositions (i.e., otherthan phosphate builders), the present invention provides high-volumeproduction of crisp, controlled density, uniforrnly sized granularsynthetic detergent compositions.

The foregoing objects and improvements are achieved by the presentinvention which in its method embodiments comprises a continuous methodfor spray drying large volumes of a synthetic detergent slurry in aspray-drying tower and producing a granular synthetic detergentcomposition having controlled density and uniform reduced particle sizewith minimum production of dust particles and other vaporous effluentscomprising the following steps:

I. preparing an aqueous synthetic detergent slurry having about percentto 50 percent by weight water and the balance 50 percent to 90 percentsolids content being comprised of at least one organic syntheticdetergent, and at least one detergency builder selected from organic orinorganic builders or mixtures thereof;

2. establishing within the chamber of the spray tower (a) acylindrically shaped drying zone with the axis of the chamber by passingheated drying air upwards through the chamber in a cyclonic motion and(b) a low-pressure zone comprising a concentric vortex tube which isformed along the axis of the chamber;

3. continuously spraying countercurrently from 30 percent to 80 percentof said synthetic detergent slurry directly into the cylindricallyshaped drying zone at the point below a 190 F. isotherm and above aboiling point isotherm said spraying being achieved with atomizingnozzles substantially uniformly spaced in a horizontal plane through thecylindrical drying zone thereby providing that substantially each of thesprays disintegrates into particles within said cylindrical drying zone;

4. continuously spraying countercurrently the balance of said syntheticdetergent slurry directly into the cylindrically shaped drying zone at apoint above the 190 F. iso therm by means of at least one level ofatomizing nozzles substantially uniformly spaced in a horizontal planethrough the cylindrical drying zone, thereby providing thatsubstantially each of the sprays disintegrates into particles withinsaid cylindrical drying zone, whereby the only disintegrated particlesentering the low-pressure vortex tube are those incidentally carried bythe cyclonic motion of the drying gas.

The apparatus aspects are apparent from the detailed discussion below:

DRAWINGS Attention is drawn to the two figures comprising part of thisapplication.

FIG. 1 is a side elevational view illustrating a multilevel spray-dryingtower incorporating the present invention.

FIG. 2 is an enlarged cross-sectional detail taken along line 22 of FIG.I and serving to illustrate the cylindrically shaped drying zone, theconcentric vortex tube, and the manner in which the atomizing nozzlesare substantially uniformly spaced in a horizontal plane through thecylindrical drying zone.

The spray-drying tower apparatus illustrated in the drawing is nowdescribed in order to present both the apparatus embodiments and methodembodiments of the present invention.

Referring to FIG. 1, box diagram 10 represents a crutcher slurrypreparation. This is intended to include an entire conventionalcrutching or mixing system together with means, 11, for passing it to ahigh-pressure pump, 12. Conventional crutching systems are well familiarto those skilled in the art and typically include storage hoppers forraw materials, conveyors, scales, a crutcher, a drop tank, and the like.For purposes of the present invention, the slurry is comprised of 10percent to 50 percent water by weight and the balance 50 percent topercent solids content. The solids content is made up of the ingredientswhich constitute the formula for the desired granular syntheticdetergent composition. The crutcher slurry contains at least one organicsynthetic detergent of an anionic, nonionic, arnpholytic, orzwitterionic type; preferably anionic detergents are employed. Adetailed description of suitable detergent materials is givenhereinafter. At least one detergency builder is added to the crutcherslurry. It can be of an organic or inorganic type, again as described indetail elsewhere in this specification. It is common to employ mixturesof different detergents and different builder materials in preparing theslurry.

The slurry is passed through suitable pipes, conduits and the likedesignated at 11 by means of a high-pressure pump, 12. Any suitable pumpcan be used but preferably those capable of providing pressure in therange of 400 to 2,000 p.s.i.

Although the invention is susceptible of variation and adaptation withrespect to many of the particulars such as the flow ducts, an airinjection system is shown at 14. Basically this is a traditional densitycontrol means rather universally employed. While this is an optionalembodiment is terms of this invention, it is a helpful device and itsemployment is recommended. The amount of air injection into the systemfrom this ancillary source should range from 0 to standard cubicft./min., and preferably 0 to I00 standard cubic ft./min.

From the air injection step, the aerated slurry is passed to thespray-drying tower chamber, 39, simultaneously by feedline 13 to nozzlearms 15 and atomizing nozzles 16, by feedline 17 to atomizing nozzles18, and by feed 19 to atomizing noules 20.

The spray-drying tower is illustrated as comprising a spraydryingchamber 39, having the atomizing nozzles uniformly and discretely spacedtherein; a hot-air duct 21, passing to a plenum 22 for distributing thehot air into the chamber 39 by a means of tuyeres 23. The hot air bythis arrangement, and this is critical to the optimum practice of thepresent invention, is introduced into the chamber 39, in the form ofcyclonic motion. For best results the hot air should have a temperaturein the range of 300 and 800 F., preferably 400 to 700 F. and beintroduced at a rate of 1,000 lbs/min. to 6,000 lbs/min. preferably2,000 to 4,000 lbs/min. The cyclonic motion of the heated drying air hasan important bearing on the vertical spacing of the multilevels ofnozzles l6, l8 and 20, as well as the horizontal spacing of theatomizing nozzles uniformly within each spraying level.

At the base of the spray tower is a cone 24, valve 25, and conveyormeans 26, by which the dried granules are removed. The conveyor means26, passes the dried granules to a sifting screen 27, at which pointcoarse granules 28, are gathered and can be recycled by line 30 to thecrutcher slurry, I0. The desired product granules 29 are collected andpackaged or stored.

The top of the spray tower is equipped with exhaust means 31. Leadingfrom the exhaust exit is a line 32 designated to lead fine particles toan appropriate treatment or recovery area 33. From this point the spentexhaust gases are passed into the atmosphere.

Within spray chamber 39 there is designated a cylindrical spray-dryingzone 40 and a vortex tube 38. The parameters for the cylindricalspray-drying zone 40 and the vortex tube 38 are determined by thecyclonic effect of the rising heated air. It is important to thepractice of this invention that the sheets of sprays from the atomizingnozzles disintegrate in the designated cylindrical drying zone. It hasbeen discovered that if this condition is met, the optimum results areobtained in terms of increased production rates, controlled density,uniform particle size, reduced stickiness of the granules, reducedproduction of fine (dust) and coarse granules, and reduced vaporouseffluents. The size of the vortex tube can vary depending on severalfactors including velocity of the cyclonic heated drying air, size ofapparatus etc. The important consideration with respect to the vortextube is that it is an area of decreased pressure and any particlesfreshly sprayed into this vortex tube area are not subjected to thedesirable optimum drying influences created by the critical horizontaland vertical alignments of the levels of nozzles as well as theircritical uniform horizontal spacing within each level.

Freshly sprayed particles entering into the low-pressure region of theinternal concentric vortex tube fall prematurely through the tower andinterfere with the objectives of the in ventions identified above. Itwas consequently discovered that, in addition to a critical verticalspacing of the levels of atomizing nozzles discussed below, thehorizontal spacing of the nozzles must be such that the sheets of sprayfrom each noule must disintegrate within the prescribed cylindricalspray-drying zone; care must be taken that the sheets of spray are notsprayed into the vortex tube. It is in this context that the termdirectly into the cylindrical spray-drying zOne is used to indicate theimportance of avoiding spraying into the vortex tube area.

FIG. 1 also embodies another essential embodiment of this invention,namely the vertical spacing of the plurality of levels of spray nozzles.Special consideration is to be given the lowest level of the spraynozdes for its positioning is fundamental to achieving and optimizingthe objectives noted above. In FIG. 1, the lowest level is designated byfeedline I9 and atomizing nozzles 20.

This lowest level of spray nozzles is essentially located at or below a190 F. isotherm, 41 and above a boiling point isotherm. Isotherms arewell understood temperature profiles within a spray-drying chamberinvolving heated drying air. It is necessary that the freshly sprayedparticles at this lowest level be exposed to temperatures in the rangeof 190 F. to about 2l0220 F. This permits rapid puffing of the granuleswith a corresponding reduction in density. The particle size iscontrolled because the rapid evaporation which occurs is not so rapid asto explode the granules and produce inordinate amounts of fine powders.Large amounts of fines would tend to increase the density of the finalgranular product. In addition to the release of substantial amounts ofwater in this space as a result of rapid drying there is also asignificant production of expanding and released gases. Both thereleased water in the form of steam and the released gases pass upthrough the tower with the heated drying gas. This type of a dynamicsystem has not previously been known. The beneficial effects have neverpreviously been recognized.

Referring to FIG. I it is seen that the F. isotherm, 41 and the lowestlevel of spray nozzles are positioned in zone A 35. The size of thiszone is, of course, susceptible of variation and modification due toadjustment of any of several processing variables. The significance ofdesignating the 190 F. isotherm, 4] and the lowest level of spray noules20, is to emphasize the essential space relationships of these twofactors. The balance of the spray tower is designated as zone B, 34. Inthis region the drawing illustrates two levels of spray nozzles, 16 and18. It is to be noted that while two levels are shown, only one needs tobe present to provide the benefits of this invention. Thus it is withinthe contemplation of this invention to embody as few as two levels ofspray nozzles, for example 16 and 20, or 18 and 20. It is possible,however, to have levels of nozzles in zone B, 34 spaced at 8-footintervals. Thus, if Zone B were 50 feet high there would be space for asmany as six levels of atomizing nozzles. In any event, an essentialfeature is to provide means for spraying from 30 percent to 80 percentof the detergent slurry in zone A 35, i.e., below a 190 F. isotherm andabove a boiling point isotherm. The reason for remaining above a boilingpoint isotherm has been implied above. Exceeding the boiling point ofthe slurry would have an adverse effect on the drying rate, productionof fines and possible charting of the product.

It is necessary to provide at least 30 percent of the slurry into thelowest level to obtain the maximum benefit of the invention. Whileamounts greater than 80 percent can be fed to this level, it ispreferred to remain below 80 percent to balance the several processingconditions involved, rate of addition of the heated drying gas, thecyclonic effect, the rate of drying and the like. Optimum results areobtained when from 35 percent to 70 percent by weight is sprayed intothe lowest level.

When only two levels of nozzles are used, the top level can be desirablylocated in a zone in the tower where temperatures range from F. to F.

When a third level is to be used, it should preferably be spacedsubstantially equidistant the top level and the bottom level.

In FIG. I, a variation of the spacing of the spray nozzles is depictedby positioning them adjacent to the wall of the spraydrying chamber. Afeedline 36 is indicated passing slurry to such nozzles. In such aposition, care needs to be exercised that the spray from the nozzles isdirected into the drying zone to avoid sticking to the vertical wall ofthe chamber.

In FIG. 2, taken along 2-2 of FIG. I, the substantially unifonn spacingof atomizing nozzles 20 is illustrated. These nozzles 20 are seen to bepart of a manifold ring 42 leading to feedline 19. It is important tospace the spray nozzles throughout the tower in such a position thatthey are not too close to the chamber wall 39 or too close to thelow-pressure vortex tube, 38. If freshly sprayed slurry contacts thewall, it can tend to stick to the wall and build up large deposits.These must be removed with difficulty and they can obstruct thedesirable gas flow patterns which the method and apparatus are designedto achieve.

In FIG. 2, the plenum is indicated as 22 and the conveyor, 26 leads awayfrom the tower.

The following examples illustrate the present invention. Variations andmodifications can be made in the examples without deviating from hepractices taught and contemplated by the present invention. Data ispresented in tabular form between two-level and three-level embodimentsof this invenm g y llkyl bwww sulfonale P ium su ate [1.5 parts t on andcomparisons made with ordinary single level opera now my id L pm!Hardened marine fatty acid 0.5 parts EXAMPLE Sodium silicate 93 Pam 5ST? 38.4 parts tic d l of the followin a roximate "TANG P A synfileetergent g pp Minors (CMC and brighteners) 1.0 parts composition wasprepare 36.7 Pam Pam, Spray drying was performed under the followingconditions with these results: Sodium tellow elkyl sulfate 9. 2 10Sodium dodecyl alkyl benzene sullonet-e- 7. 6 Sodium sulfate l3. 0

0 2-2 8-8 g Spray nozzle arrangement 3:50: r 2 amide R NH! 1 grogucgmrzlstpgefiercent 5 g. 8 49 r A to no la e 5. our 9, 00 "iihylnilliiilfl'i .fffflfffiiflflfff.li .T.". f1- 0. 6 Product density,0184100111- Sodium silicate 7 0 Percent on 14 mesh 5. 5 8 Sodiummpolyphosphate (STP) 6 Coarse recycle level (measured), lbs/hour... 2,880 4, 680 Sodium mmlomammw (NTA) m 4 Injection air level, approximatepercent- 29 30 Water 40. 8 T 1 u t i c t o F g -g-g M ower r e a rampere ure mom (CMC and brightenem) 1 0 Tower exhaust air temperature, F170 181 e Product limitation The slurry was spray dned under thefollowing conditions High Pressure p p pressure. p 090 1.050 wlth theseresuhs: Inability to ump more material to toweri1 1 M groduct stic Jcoarse recycle too high to and e. Spray nozzle arrangement. 4-22 5-35 435 Final product moisture,

percent s. 5 s. 5 7. 0 This example also demonstrates multileveleffectiveness in E8333 fifgfi i g; ggg 2? rates, density, coarserecycle, etc. over a single-level system. Percent on 14 mesh screen,

percent 7 3 5. 5 EXAMPLE IV Coarse recycle level (observanon) Light;Moderate Heavy Injection air level, approximate percent (54 S c 1 (52 Sc f? (54 512L113), Sodium dodecyl alkyl benzene sulfonale 16.8 partsTower inlet air temperature, H o 50 50 55 Sodium silicate 7.0 partsTower exhaust air tempera- ST? 33.6 parts ture, 185 186 90 NTA-Na, 12.5parts g i' g gg ug ggg g e-s (I) (I) (a) Minors (CMC and brighteners)1.1 parts sire: p.s.i 1, 000 1, one 1, 050 36.0 parts 1 nable to conveyproduct away from tower fast enough.

Come031918leiveklggwglllggandle 40 Sprayed dried under the followingconditions with these The nozzles were uniformly spaced at each level.The l changes in rate, density, coarse recycle amounts are allsignificant.

This example produced an excellent detergent product having reducedphosphate level. it demonstrates the efficacy of a Spray nozzlearrangement mixed anionic active system used with a builder mixture ofProduct moisture, percent" ST? and NTA. X0gl1CllBte,1libS./h0lfi66 r0 ucens y, ozs. EXAMPLE Percent on 14 mesh screen.- Coarse recycle level,lbs/hour A synthetic detergent slurry was prepared similar to exarn-Fine recycle (from exhaust system),

pie 1 but without NTA-Na Instead the STP level was inggg '155 5 555553:

creased to 47 parts. Spray drying was performed using the fol- Towerexhaust air temperature,

Production limitation lowmg condmons: High pressure pump pressure,p.s.l-

3-3 l Drying capacity oi the spray tower (inlet temperature at maximum).

Spray nozzle angement- 535' ilfgqq g jjiq l mgsezwhecarmwujetq ongestFinaltproduct moisture, per- 2 3 can l 12. 7 12. 0 ggggg: f f -ggfim t229 Q2 The decreased amount of fines produced with the three- P rcent r?14 121351.; 8 Kg level system of the present invention is very marked.Coarse recycle level Moderate Heavy in this example the ST? or the NTAcan be replaced with an n ectlon arr level, approxi equal amount byweight of sodium citrate, sodium mellltate,

mate percent 8 70 94 4 1 s i-m.) (86 s.o.i.m.) sodium oxydlacetate,SOdlUlTi oxydisucclnate with satisfactory Tower inlet air temperature, 5

F e75 077 678 Tlzwer gxgaust air tempera- 179 180 1 In each of theseexamples, the production of fines was ure l Produ'ction limitation m (a)8; reduced by approximately 50 percent. The product was free Highpressure pump presflowing, uniformly sized granules.

975 975 11000 Additional tests were performed convincingly showing theyerg hgar y. d t t 1 f t disadvantages of spraying fresh particles tooclose to the I13 y 0 pump e ergen S urry 8S 8!". 3 Coarse recycle levelsmo high to handm Density high. chamber wall or into the vortex zone ofdecreased pressure. 4 Coarse recycle levels too high to handle. Productdensity high. EXAMPLE V EXAMPLE The following slurry was prepared:

A synthetic detergent slurry of the following composition was prepared:Tndecyl benzene suli'onete P Condenlation product of coconut alcohol and6 moles of ethylene oxide (CNAEJ 3.3 parts Sodium tripolyphosphate (STP)4.8 parts Sodium nitrilotriacetate (NTA-Na,) 25.0 parts Sodium silicatesolids 10.6 parts Sodium sulfate 28.1 parts Hardened marine fatty acid0.5 parts Tallow fatty acid 1.5 parts Minors (CMC and brightenen) 1.0parts Water 35.2 parts Spray drying was done with the followingdifferent nozzle configurations with the results indicated:

These show that: (1) Up to 30 percent gain in tower rate is provided bythe three-level nozzle arrangement; (2) Drying conditions are lesssevere and product quality is guarded in that the STP hexahydrate is notbroken down as much when multilevel nozzles are used: (3) Processing iscontrollable.

The hexahydrate is primarily formed in the slurry prior to spraying intothe drying tower. Therefore, the lower hexahydrate level in the productmade with nozzles all at one level indicates more severe dryingconditions. The analysis of phosphate species in the productsubstantiate this in that the higher levels of pyro and ortho phosphatesin the product with single-level nozzles would result from overdryingthe product (phosphate reversion).

Noteworthy also is that this formulation with all the nozzles at onelevel could not be produced at a higher rate because the product becametoo sticky to handle. The three-level operation was not rate limited,and was essentially free of stickiness.

In each of the foregoing examples, the lowest level was positioned at apoint below a 190 F. isotherm and above a boiling point isotherm. Theamount sprayed through each nozzle was approximately the same. Thepercentage sprayed into each zone is readily ascertainable bycalculation. The amount sprayed into the lowest level was always in therange of 30 percent to 80 percent of the slurry produced.

With the present invention it is possible to prepare synthetic detergentcompositions of varied formulations.

The organic detergent can be selected from well-known classes ofsynthetic detergents including anionic, nonionic, ampholytic andzwitterionic detergents. These are illustrated by the following listedmaterials.

A. ANlONlC SOAP AND NONSOAP SYNTHETIC DETERGENTS This class ofdetergents includes ordinary alkali metal soaps such as the sodium,potassium, ammonium and alkylolammonium salts of higher fatty acidscontaining from about eight to about 24 carbon atoms and preferably fromabout to about 20 carbon atoms. Suitable fatty acids can be obtainedfrom natural sources such as, for instance, from plant or animal esters(e.g., palm oil, coconut oil, babassu oil, soybean oil, castor oil,tallow, whale and fish oils, grease, lard, and mixtures thereof). Thefatty acids also can be synthetically prepared e.g., by the oxidation ofpetroleum, or by hydrogenation of carbon monoxide by the Fischer-Tropschprocess). Resin acids are suitable such as rosin and those resin acidsin tall oil. Napthenic acids are also suitable. Sodium and potassiumsoaps can be made by direct saponification of the fats and oils or bythe neutralization of the free fatty acids which are prepared in aseparate manufacturing process. Particularly useful are the sodium andpotassium salts of the mixtures of fatty acids derived from coconut oiland tallow, i.e., sodium or potassium tallow and coconut soap.

This class of detergents also includes water-soluble salts,

o particularly the alkali metal salts of organic sulfuric reactionproducts having in their molecular structure an alkyl radical containingfrom about eight to about 22 carbon atoms and a sulfonic acid orsulfuric acid ester radical. (Included in the term alkyl is the alkylportion of higher acyl radicals.) Examples of this group of syntheticdetergents which form a part of the preferred built detergentcompositions of the present invention are the sodium or potassium alkylsulfates, especially those obtained by sulfating the higher alcohols (C-C carbon atoms) produced by reducing the glycerides of tallow orcoconut oil; sodium or potassium alkyl benzene sulfonates, in which thealkyl group contains from about nine to about 15 carbon atoms, instraight-chain or branched-chain configuration, e.g., those of the typedescribed in US. Pat. Nos. 2,220,099 and 2,477,383 (especially valuableare linear straight chain alkyl benzene sulfonates in which the averageof the alkyl groups is about 13 carbon atoms abbreviated hereinafter asC LAS); sodium alkyl glyceryl ether sulfonates, especially those ethersof higher alcohols derived from tallow and coconut oil; sodium coconutoil fatty acid monoglyceride sulfonates and sulfates; sodium orpotassium salts of sulfuric acid esters of the reaction product of onemole of a higher fatty alcohol e.g., tallow or coconut oil alcohols) andabout 1 to 6 moles of ethylene oxide; sodium or potassium salts of alkylphenol ethylene oxide ether sulfate with about 1 to about 10 units ofethylene oxide per molecule and in which the alkyl radicals containabout eight to about 12 carbon atoms.

Additional examples of anionic nonsoap synthetic detergents which comewithin the terms of the present invention are the reaction product offatty acids esterified with isethionic acid and neutralized with sodiumhydroxide where, for example, the fatty acids are derived from coconutoil; sodium or potassium salts of fatty acid amide of methyl tauride inwhich the fatty acids, for example, are derived from coconut oil. Otheranionic synthetic detergents of this variety are set forth in US. Pat.Nos. 2,486,921; 2,486,922; and 2,396,278.

Still another anionic synthetic detergents include the class designatedas succinamates. This class includes such surface active agents asdisodium N-octadecylsulfo succinamate; tetrasodium N-( l,Z-dicarboxyethyl)-N-octadecyl-sulfo-succinamate; diamyl ester of sodiumsulfosuccinic acid; dihexyl ester of sodium sulfosuccinic acid; dioctylester of sodium sulfosuccinic acid.

Anionic phosphate surfactants are also useful in the present invention.These are surface active materials having substantial detergentcapability in which the anioic solubilizing group connecting hydrophobicmoieties is an oxy acid of phosphorus. The more common solubilizinggroups, of course, are SO l-l, SO;l'l, and CO,l-1. Alkyl phosphateesters such as (R-O),PO,l-l and ROPO H, in which R represents an alkylchain containing from about eight to about 20 carbon atoms are useful.

These esters can be modified by including in the molecule from one toabout 40 alkylene oxide units, e.g., ethylene oxide units. Formulae forthese modified phosphate anionic detergents are in which R represents analkyl group containing from about eight to 20 carbon atoms, or analkylphenyl group in which the alkyl group contains from about eight to20 carbon atoms, and M represents a soluble cation such as hydrogen,sodium, potassium, ammonium or substituted ammonium; and in which n isan integer from one to about 40.

A specific anionic detergent which also has been found excellent for usein the present invention is described more fully in the US. Pat. No.3,332,880 of Phillip F. Pflaumer and Adriaan Kessler, issued July 25,1967, titled Detergent Composition. This detergent comprises by weightfrom about 30 percent to about 70 percent of component A, from about 20percent to about 70 percent of component B, and from about 2 percent toabout 15 percent of component C, wherein:

a. said component A is a mixture of double-bond positional isomers ofwater-soluble salts of alkene-l-sulfonic acids containing from about 10to about 24 carbon atoms, said mixture of positional isomers includingabout 10 percent to about 25 percent of an alpha-beta unsaturatedisomer, about 30 percent to about 70 percent of a beta-gamma unsaturatedisomer, about 5 percent to about 25 percent of a gamma-delta unsaturatedisomer, and about 5 percent to about percent of a delta-epsilonunsaturated isomer;

b. said component B is a mixture of water-soluble salts ofbifunctionally substituted sulfur-containing saturated aliphaticcompounds containing from about 10 to about 24 carbon atoms, thefunctional units being hydroxy and sulfonate radicals with the sulfonateradical always being on the terminal carbon and the hydroxyl radicalbeing attached to a carbon atom at least two carbon atoms removed fromthe terminal carbon atom, at least 90 percent of the hydroxy radicalsubstitutions being in the three, four, and five positions; and

c. said component C is a mixture comprising from about 30 percent to 95percent water-soluble salts of alkene disulfonates containing from about10 to about 24 carbon atoms and from about 5 percent to about 70 percentwater-soluble salts of hydroxy disulfonates containing from about 10 toabout 24 carbon atoms, said alkene disulfonates containing a sulfonategroup attached to a terminal carbon atom and a second sulfonate groupattached to an internal carbon atom not more than about six carbon atomsremoved from said terminal carbon atom, the alkene double bond beingdistributed between the terminal carbon atoms and about the seventhcarbon atoms, said hydroxy disulfonates being saturated aliphaticcompounds having a sulfonate radical attached to a terminal carbon, asecond sulfonate group attached to an internal carbon atom not more thanabout six carbon atoms removed from said terminal carbon atom, and ahydroxy group attached to a carbon atom which is not more than aboutfour carbon atoms removed from the site of attachment of said secondsulfonate group.

B. NONIONIC SYNTHETlC DETERG ENTS Nonionic synthetic detergents may bebroadly defined as compounds produced by the condensation of alkyleneoxide groups (hydrophilic in nature) with an organic hydrophobiccompound, which may be aliphatic or alkyl aromatic in nature. The lengthof the hydrophilic or polyoxyalkylene radical which is condensed withany particular hydrophobic group can be readily adjusted to yield awater-soluble compound having the desired degree of balance betweenhydrophilic and hydrophobic elements.

For example, a well-known class of nonionic synthetic detergents is madeavailable on the market under the trade name of P1uronic. Thesecompounds are formed by condensing ethylene oxide with a hydrophobicbase formed by the condensation of propylene oxide with propyleneglycol. The hydrophobic portion of the molecule which, of course,exhibits water insolubility, has a molecular weight of from about 1,500to 1,800. The addition of polyoxyethylene radicals to this hydrophobicportion tends to increase the water solubility of the molecule as awhole and the liquid character of the product is retained up to thepoint where polyoxyethylene content is about 50 percent of the totalweight of the condensation product.

Other suitable nonionic synthetic detergents include:

1. The polyethylene oxide condensates of alkyl phenols, e.g., thecondensation products of alkyl phenols having an alkyl group containingfrom about six to 12 carbon atoms in either a straight-chain orbranched-chain configuration, with ethylene oxide, the said ethyleneoxide being present in amounts equal to 5 to 25 moles of ethylene oxideper mole of alkyl phenol. The alkyl substituent in such compounds may bederived from polymerized propylene, diisobutylene, octene, or nonene,for example.

2. Those derived from the condensation of ethylene oxide with theproduct resulting from the reaction of propylene oxide and ethylenediarnine. For example, compounds containing from about 40 percent toabout percent polyoxyethylene by weight and having a molecular weight offrom about 5,000 to about 11,000 resulting from the reaction of ethyleneoxide groups with a hydrophobic base constituted of the reaction productof ethylene diamine and excess propylene oxide, said base having amolecular weight of the order of 2,500 and 3,000, are satisfactory.

3. The condensation product of aliphatic alcohols having from eight to22 carbon atoms, in either straight-chain or branched-chainconfiguration, with ethylene oxide, e.g., a coconut alcohol-ethyleneoxide condensate having from five to 30 moles of ethylene oxide per moleof coconut alcohol, the coconut alcohol fraction having from 10 to 14carbon atoms.

4. Nonionic detergents include nonyl phenol condensed with either about10 or about 30 moles of ethylene oxide per mole of phenol and thecondensation products of coconut alcohol with an average of either about5.5 or about 15 moles of ethylene oxide per mole of alcohol and thecondensation product of about 15 moles of ethylene oxide with 1 mole oftridecanol.

Other examples include dodecylphenol condensed with 12 moles of ethyleneoxide per mole of phenol; dinonylphenol condensed with 15 moles ofethylene oxide per mole of phenol; dodecyl mercaptan condensed with 10moles of ethylene oxide per mole of mercaptan; bis-(N-2-hydroxyethyl)lauramid; nonyl phenol condensed with 20 moles of ethylene oxide permole of nonyl phenol; myristyl alcohol condensed with 10 moles ofethylene oxide per mole of myristyl alcohol; lauramide condensed with 15moles of ethylene oxide per mole of lauramide, and diisooctylphenolcondensed with 15 moles of ethylene oxide.

5. A detergent having the formula RRR N 0 (amine oxide detergent)wherein R is an alkyl group containing from about 10 to about 28 carbonatoms, from zero to about two hydroxy groups and from zero to about fiveether linkages, there being at least one moiety of R is an alkyl groupcontaining from about 10 to about 18 carbon atoms and zero etherlinkages, and each R and R are selected from the group consisting ofalkyl radicals and hydroxyalkyl radicals containing from one to aboutthree carbon atoms;

Specific examples of amine oxide detergents include:dimethyldodecylamine oxide, dimethyltetradecylamine oxide,ethylmethyltetradecylamine oxide, cetyldimethylamine oxide,dimethylstearylamine oxide, cetylethylpropylamine oxide,diethyldodecylamine oxide, diethyltetradecylamine oxide,dipropyldodecylamine oxide, bis-( 2-hydrox yethyl)dodecylamine oxide,bis-(2-hydroxyethyl)-3-dodecoxy-l-hydroxypropylamine oxide,(2-hydroxypropyl)methyltetradecylamine oxide, dimethyloleyamine oxide,dimethyl- (2-hydroxydodecyl)amine oxide, and the corresponding decyl,hexadecyl and octadecyl homologs of the above compounds.

6. A detergent having the formula RRRP O (phosphine oxide detergent)wherein R is an alkyl group containing from about to about 28 carbonatoms, from zero to about two hydroxy groups and from zero to about fiveether linkages, there being at least one moiety of R which is an alkylgroup containing from about 10 to about 18 carbon atoms and zero etherlinkages, and each of R and R are selected from the group consisting ofalkyl radicals and hydroxyalkyl radicals containing from one to aboutthree carbon atoms.

Specific examples of the phosphine oxide detergents include:dimethyldodecylphosphine oxide, dimethyltetradecylphosphine oxide,ethylmethyltetradecylphosphine oxide, cetyldimethylphosphine oxide,dimethylstearylphosphine oxide, cetylethylpropylphosphine oxide,diethyldodecylphosphine oxide, diethyltetradecylphosphine oxide,dipropyldodecylphosphine oxide, bis-(hydroxymethyl)dodecylphosphineoxide, bis-(2-hydroxyethyl)- dodecylphosphine oxide,(2-hydroxypropyl)methyltetradecylphosphine oxide, dimethyloleylphosphineoxide, and dimethyl-(2-hydroxydodecyl)phosphine oxide and thecorresponding decyl, hexadecyl, and octadecyl homologs of the abovecompounds.

7 A detergent having the formula (sulfoxide detergent) wherein R is analkyl radical containing from about 10 to about 28 carbon atoms, fromzero to about five ether linkages and from zero to about two hydroxylsubstituents at least one moiety of R being an alkyl radical containingzero ether linkages and containing from about 10 to about 18 carbonatoms, and wherein R is an alkyl radical containing from one to threecarbon atoms and from one to two hydroxyl groups: octadecyl methylsulfoxide, dodecyl methyl sulfoxide, tetradecyl methyl sulfoxide,3-hydroxytridecyl methyl -sulfoxide, 3-methoxytridecyl methyl sulfoxide,3- hydroxy-4-dodecoxybutyl methyl sulfoxide, octadecyl 2- hydroxyethylsulfoxide, dodecylethyl sulfoxide.

C. AMPHOLYTIC SYNTHETIC DETERGENTS Ampholytic synthetic detergents canbe broadly described as derivatives of aliphatic or aliphaticderivatives of heterocyclic secondary and tertiary amines, in which thealiphatic radical may be straight-chain or branched and wherein one ofthe aliphatic substituents contains from about eight to 18 carbon atomsand at least one contains an anionic water-solubilizing group, e.g.,carboxy, sulfo, sulfato, phosphato, or phosphono, Examples of compoundsfalling within this definition are sodium 3-(dodecylamino)-propionate,sodium 3- (dodecylamino)propane-l-sulfonate, sodium 2-(dodecylamino)ethyl sulfate, sodium 2-(dimethylamino)octadecanoate,disodium 3-(N-carboxymethyldodecylamino)- propane-l-sulfonate, disodium2-(oleylamino)ethyl phosphate, disodium3-N-methylhexadecylamino)propyl-1- phosphonate, disodiumoctadecyl-iminodiacetate, sodium 1- carboxymethyl-2-undecylimidazole,disodium 2-[N-( 2- hydroxyethyl)octadecylamino 1N,Nbis-(2hydroxyethyl)-2-.

sulfato-3-dodecoxypropylamine.

D. ZWITTERIONIC SYNTHETIC DETERGENTS LII dimethylN-dodecylammonio)propionate, 2-(N,N-dimethyl- N-octadecylammonio)-ethylsulfate, Z-(trimethylammonio)ethyl dodecylphosphonate, ethyl3-(N,N-dimethyl-N- dodecylammonio )-propylphosphonate, 3-(P,P-dimethyl-P- dodecylphosphonio)propane-1-sulfonate,2-(S-methyl-S-tert.-

hexadecyl-sulfonio )ethanel -sulfonate, 3-( S-methyl-S- dodecylsulfonic)propionate sodium 2-( N ,N-dimethyl-N- dodecylammonio )ethylphosphonate, 4-(S-methy1-S- tetradecylsulfonio)butyrate, 1-(2-hydroxyethyl )-22-undecylimidozolium- 1 -acetate, Z-(trimethylammonio)-octadecanoate, and3-(N,N-bis-(2-hydroxyethyl)-N-octodecylammonio)-2-hydroxypropane-l-sulfonate.Some of these detergents are described in the following U.S. Pat. Nos.:2,129,264; 2,178,353; 2,774,786; 2,813,898; and 2,828,332.

The builders can be any organic or inorganic builders.

Examples of suitable water-soluble, inorganic alkaline detergencybuilder salts are alkali metal carbonates, borates, phosphates,polyphosphates, bicarbonates, silicates and sulfates. Specific examplesof such salts are sodium and potassium tetraborates, perborates,bicarbonates, carbonates, tripolyphosphates, pyrophosphates,orthophosphates and hexametaphosphates. Sodium sulfate, although notclassed as an alkaline builder salt, is included in this category.

Examples of suitable organic alkaline detergency builder salts are: 1)Water-soluble aminopolycarboxylates, e.g., sodium and potassiumethylenediaminetetraacetates, nitrilotriacetates andN-(2-hydroxyethyl)-nitrilodiacetates; (2) Water-soluble salts of phyticacid, e.g., sodium and potassium phytates-See U.S. Pat. No. 2,739,942;(3) Water-soluble, polyphosphonates, including specifically, sodium,potassium and lithium salts of ethane-l-hydroxy-l,l-diphosphonic acid,sodium, potassium and lithium salts of methylene diphosphonic acid,sodium, potassium and lithium salts of ethylene diphosphonic acid, andsodium, potassium and lithium salts of ethane-1,1,2-triphosphonic acid.Other examples include the alkali metal salts of ethane-Z-carboxy-l ,1-diphosphonic acid, hydroxymethanediphosphonic acid, carbonyldiphosphonicacid, ethane- 1 -hydroxy-l l ,2- triphosphonic acid, ethane-2-hydroxy-1,1 ,Z-triphosphonic acid, propane-1,1,3,3--tetraphosphonic acid,propane-1,12,3- tetraphosphonic acid, andpropane-1,2,2,3-tetraphosphonic acid; (4) Water-soluble salts ofpolycarboxylate polymers and copolymers as described in the copendingapplication of Francis L. Diehl, Ser. No. 269,359, filed Apr. 1, 1963,now U.S. Pat. No. 3,308,067. Specifically, a detergent builder materialcomprising a water-soluble salt of a polymeric aliphatic polycarboxylicacid having the following structural relationships as to the position ofthe carboxylate groups and possessing the following prescribed physicalcharacteristics: (a) a minimum molecular weight of about 350 calculatedas to the acid form; (b) an equivalent weight of about 50 to aboutcalculated as to acid form; (c) at least 45 mole percent of themonomeric species having at least two carboxyl radicals separated fromeach other by not more than two carbon atoms; (d) the site of attachmentof the polymer chain of any carboxyl-containing radical being separatedby not more than three carbon atoms along the polymer chain from thesite of Karim Eat of the next carboxyl-containing radical. Specificexamples are polymers of itaconic acid, aconitic acid, maleic acid,mesaconic acid, fumaric acid, methylene malonic acid, and citraconicacid and copolymers with themselves and other compatible monomers suchas ethylene; and (5) mixtures thereof.

Mixtures of organic and/or inorganic builders can be used and aregenerally desirable. One such mixture of builders is disclosed in thecopending application of Burton H. Gedge, Ser. No. 398,705, filed Sept,23, 1964, now U.S. Pat. No, 3,392,121, e.g., ternary mixtures of sodiumtripolyphosphate, sodium nitrilotriacetate and trisodiumethane-l-hydroxy-l,ldiphosphonate. The above-described builders can alsobe utilized singly in this invention. Especially preferred builders thatcan be used singly or in combination in this invention include sodiumperborate and sodium tripolyphosphate. Sodium tripolyphosphate andsodium perborate can be used in combination in a weight ratio range offrom about 95:5 to about 50:50.

In addition, other builders can be used satisfactorily such aswater-soluble salts of mellitic acid, citric acid, pyromellitic acid,benzene pentacarboxylic acid, oxydiacetic acid, oxydisuccinic acid.

All of the percentages and proportions used in describing the presentinvention are by weight unless otherwise specified.

The spray tower method described herein is the subject of anothercommonly assigned patent application Ser. No. 60,01 1, filed July 31,1970 entitled Multi-Level Spray Drying Method," by Robert P. DavisMichael S. Haines and John A. Sagel.

While the multilevel spray method of this invention gives overall finerproduct, the control of density is not lost in that the density of theindividual sieve fractions is lighter. This is shown in the followingparticle size (sieve) distribution and the bulk density of theindividual fractions:

Fractions Separated 3 level 3 at 8 feet, 3 at 22 feet, 4 at 35 feet 1level 9 at 8 feet This date was obtained from product prepared inexample ll above.

The foregoing description of the present invention has been presenteddescribing certain operable and preferred embodiments. It is notintended that the invention should be so limited since variations andmodifications thereof will be obvious to those skilled in the art, allof which are within the spirit and scope of this invention.

What is claimed is:

l. A spray-drying tower for producing large volumes of uniformly sizedgranular synthetic detergent compositions having controlled density witha minimum production of dust particles and other vaporous efi'luents,

said tower comprising in combination,

a. a spray drying chamber,

b. means for introducing into the bottom of said spray-drying chamberand maintaining within said spray-drying chamber, a cyclonic current ofheated drying gas, said cyclonic movement being about the longitudinalaxis of said spray-drying chamber and forming a cylindrically shapeddrying zone with said axis of the chamber,

c. means for exhausting gas from the top of the spray-drying chamber,

d. at least two horizontal levels of atomizing nozzles disposed withinsaid chamber each of said levels comprising a plurality of atomizingnozzles substantially uniformly spaced in a horizontal plane throughsaid cylindrical drying zone, the vertical alignment of the lowest levelof said atomizing nozzles being at a point in the spray chamber below al F. isotherm and above a boiling point isotherm as these isotherms areformed during operation of the spraydrying tower, the balance of thelevels of atomizing nozzles being located above said lower level,

f. means for providing a synthetic detergent slurry having about l0percent to 50 percent by weight water and the balance 50 percent to 90percent solids content bein comprised 0 at least one organic syntheticdetergent, an

at least one detergency builder selected from organic or inorganicbuilders or mixtures thereof;

means for passing said synthetic detergent slurry to said plurality ofhorizontal levels of atomizing nozzles, said means passing from 30percent to 80 percent by weight of said slurry to said lowest level ofsaid atomizing nozzles and the balance of said slurry being passed tothe remaining levels of atomizing nozzles located above said lowestlevel,

h. means for removing the dried particles from the bottom of saidspray-drying chamber.

2. A spray-drying tower according to claim 1 in which the highesthorizontal level of atomizing nozzles is located near the top of thetower where temperatures in the tower range from F. to F.

3. A spray-drying tower according to claim 2 in which a third level ofuniformly distributed atomizing nozzles is spaced intermediate saidhighest level and said lowest level.

2. A spray-drying tower according to claim 1 in which the highesthorizontal level of atomizing nozzles is located near the top of thetower where temperatures in the tower range from 165* F. to 185* F.
 3. Aspray-drying tower according to claim 2 in which a third level ofuniformly distributed atomizing nozzles is spaced intermediate saidhighest level and said lowest level.